Trouble with Trolls by Jan Brett

The trolls who live on Mount Baldy want a dog. And that's where Treva's trouble with trolls begins. When she sets off with her dog, Tuffi, to visit her cousin, the greedy trolls spot Tuffi and try to kidnap him. But Treva is brave and quick-thinking. She outwits one troll after another until she reaches the very top of the mountain, where all five trolls are waiting, and they want the dog!